In power distribution networks, the control of individual items of equipment, e.g. plant items or other loads, is handled by respective digital outputs. Each such digital output typically takes the form of a switch element, which is openable and closeable to selectively permit the flow of current, e.g. from a power supply, to the item of equipment in order that the item of equipment may operate.
Each switch element may be a relay contact or a so-called high-speed high-break contact that typically consists of a relay contact arranged in parallel with an electronic switching element, such as a semiconductor switching element in the form of transistor.